This invention relates to a vehicle motion control apparatus for controlling a plane vehicle behavior, such as vehicle yaw rate, during vehicle steering operation.
It is the current practice to control the vehicle yaw rate so as to ensure good vehicle stability during vehicle steering operation. For example, Japanese Patent Kokai No. 5-170116 discloses a vehicle motion control apparatus arranged to calculate a target yaw rate value (target vehicle motion value) by providing a time lag of first order and phase advance compensation with respect to the steering wheel steering angle. A target rear road wheel steering angle value required to bring the vehicle yaw rate into coincidence with the target yaw rate value is calculated from equations of motions based on various vehicle parameters. Such vehicle motion control is advantageous in that the vehicle yaw rate occurs with no phase delay with respect to steering angle changes (FIG. 9A). Furthermore, it is possible to minimize yaw rate oscillations so as to provide good steering response and stability (FIG. 9B). Since the yaw rate converges at a fast rate in response to steering angle changes, however, the driver would feel a sense of incompatibility resulting from the accelerated rate of convergence of vehicle oscillations.